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The Effects of Shuttle Programs upon the Growth of Broilers and the Development of Immunity to Eimeria Species1
The Effects of Shuttle Programs upon the Growth of Broilers and the Development of Immunity to Eimeria Species1 H. D. CHAPMAN and A. B. HACKER Department of Poultry Sciences, University of Arkansas, Fayetteville, Arkansas 72701-1201
1993 Poultry Science 72:658-663
INTRODUCTION
Shuttle programs, in which two or more anticoccidial drugs are included in the feed during the life of a single flock of birds, are widely used in broiler production. Despite this, there is little published information upon the efficacy of such programs for the control of coccidiosis. In this study, the efficacy of nicarbazin, halofuginone, or robenidine in the starter feed, followed by the ionophore lasalocid in the grower ration, was investigated. A current practice when rearing broilers to 8 wk is to remove the anticoccidial drug from the diet approximately 2 wk
prior to slaughter (Chapman and Johnson, 1992). The effect of withdrawing medication for 1 or 2 wk upon the growth of broilers reared on lasalocid is not known and was, therefore, examined. Coccidiosis may occur following withdrawal of anticoccidial drugs, and, therefore, acquisition of immunity is desirable if long withdrawal periods are employed (McDougald and Reid, 1971). Birds reared on a shuttle program comprising nicarbazin and salinomyrin developed immunity to certain species of Eimeria (Chapman, 1992). A further objective was to investigate the development of immunity in birds reared on nicarbazin, halofuginone, or robenidine followed by lasalocid. MATERIALS AND METHODS
Received for publication October 5, 1992. Accepted for publication November 20, 1992. iPublished with the approval of the Director, Arkansas Agricultural Experiment Station. 2 Cobb 500, Cobb-Vantress, Inc., Siloam Springs, AR 72764.
Birds and Housing
Day-old male chicks of a commercial broiler strain2 were obtained from a local
658
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ABSTRACT A floor-pen trial was conducted to investigate the effects of different shuttle programs upon the growth of broilers to 8 wk of age. Nicarbazin, halofuginone, and robenidine, when included in the starter feed for 3 wk, were effective in preventing lesions due to Eimeria. The effects of medication upon performance were apparent, medicated groups gaining more weight by 6 wk and having a lower feed conversion at 6, 7, and 8 wk than the unmedicated controls. There were no significant differences in body weight at 6, 7, or 8 wk or feed conversion at 6 or 7 wk among the medicated groups, whether medication was withdrawn for 7 or 14 days. A decrease in the number of small and medium oocysts in the litter was observed as the trial progressed. Few large oocysts (Eimeria maxima) were seen in the medicated groups. Numbers of oocysts did not increase following withdrawal of medication. Birds from all medicated groups were challenged at 6 wk with oocysts of Eimeria acervulina, Eimeria maxima, or Eimeria tenella. Weight gains were similar to that of the unchallenged controls, indicating that they had acquired immunity to these species of Eimeria. (Key words: coccidiosis, shuttle program, immunity, oocysts, withdrawal of drug)
EFFECTS OF DRUGS UPON BROILERS
659
Twelve pens were randomly allocated to Treatments 1, 2, and 3, and four pens to Treatment 4. Treatments 1, 2, and 3 were given nicarbazin3 (NIC, 125 mg/kg), halofuginone 4 (HAL, 3 mg/kg), or robenidine5 (ROB, 33 mg/kg), respectively, from 0 to 3 wk, and lasalocid° (LAS, 99 mg/ kg) from 3 to 6 wk. Six pens that had been randomly preselected from each of these treatments were given lasalocid from 6 to 7 wk followed by no drug from 7 to 8 wk (designated Treatments 1A, 2A, and 3A, respectively; 1 wk of withdrawal). The remaining six pens in each treatment were given no drug from 6 to 8 wk (Treatments IB, 2B, and 3B; 2 wk of withdrawal). Treatment 4 was an unmedicated control given no drugs throughout. Roxarsone7 was included in the diet of all birds at 50 mg/kg from 0 to 6 wk.
Parasites
At 2 wk, birds were infected by including a mixture of sporulated oocysts of Eimeria acervulina, Eimeria maxima, and Eimeria tenella directly in a small quantity of feed. A total of 100,000 E. acervulina, 10,000 E. maxima, and 10,000 £. tenella were provided per bird. Oocysts were recent field isolates obtained from local broiler farms. Lesions
One bird was removed at random from each pen at 20 days (6 days after infection), necropsied, and the intestines examined for lesions due to coccidiosis by the method of Johnson and Reid (1970). The presence of oocysts of Eimeria in scrapings of the duodenum and midintestine was also recorded.
Feed
The basal diet was formulated to meet the nutritional requirements of the broiler
Oocysts in the Litter
Numbers of oocysts present in samples of litter were determined at 3,6,7, and 8 wk. Approximately 10 handfuls of surface litter were taken from four preselected pens from 3 Nicarb®, MSD AgVet, Division of Merck and Co., each treatment and placed in a plastic bag. Inc., Rahway, NJ 07065. 4 Stenorol®, Hoechst-Roussel Agri-Vet Co., The litter was weighed and suspended in 600 mL of tap water, and the oocysts Somerville, NJ 08876. 5 Robenz, American Cyanamid Co., Agricultural counted as described by Chapman (1992). Division, Wayne, NJ 07470. Oocysts were classified as either small (E. 6 Avatec®, Hoffmann-La Roche Inc., Nutley, NJ acervulina or Eimeria mitis), medium (possi07110. 7 3-Nitro®, Salsbury Laboratories, Inc., Charles City, bly E. tenella, Eimeria necatrix, or Eimeria praecox), or large (E. maxima). IA 50616.
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hatchery and assigned randomly to each of chicken (National Research Council, 1984). 40 pens (46 birds per pen). The chicks were Starter, grower, and finisher feeds were placed on new rice hulls to provide about 5 given from 0 to 3, 4 to 6, and 7 to 8 wk, to 10 cm of absorbent dry litter. Each pen respectively. A composite sample of feed was equipped with two tubular hanging was retained from each batch of feed and feeders and an automatic waterer. Ther- assayed for the concentration of drugs. mostatically controlled gas brooders and Analyses indicated that levels of the anventilation fans were used to regulate ticoccidials were within acceptable limits of temperature, and 23 h of light and 1 h of the intended concentrations. darkness was provided each day. The chicks had been vaccinated against Newcastle, Marek's, and infectious bursal Performance Data disease at the hatchery. For the 1st wk any Composite pen body weight was obbirds that died or were unable to feed tained at 3, 6, 7, and 8 wk, and total feed properly were replaced. Birds had free consumed was recorded for each age access to feed and water throughout the period. All birds that died were weighed experiment. and their body weight used to calculate feed conversion (feed consumed per unit of gain). Trial Design
660
CHAPMAN AND HACKER
Challenge Three birds were removed from each pen when the birds were 6 wk old, transferred to a clean pen, and given unmedicated feed. Three days later, each bird was weighed and challenged with either 100,000 oocysts of E. acervulina, 11,500 oocysts of E. maxima,
Statistical Analysis
Performance data for four pens (Treatment 4), 12 pens (Treatments 1,2, and 3) or six pens (Treatments 1 A, IB, 2A, 2B, 3A, and 3B) were combined for analysis. When significant treatment effects were observed, means were separated by repeated t tests using probabilities generated by the Least Squares Means option of the General Linear Models (GLM) procedure of the SAS Institute (1988). To examine differences in oocyst numbers, a split-plot design was used. When significant age by treatment interactions were observed, age means within treatments were separated using the method of least square differences.
Lesions
Lesions were found in the unmedicated controls but not in the medicated groups. A few oocysts were found in the intestines of medicated birds (Table 2). Oocysts in the Litter
Numbers of oocysts present in the litter are given in Table 3. No differences in the number of small and medium, or the number of large oocysts were found among the medicated groups (P > .05). A significant decrease in the numbers of small and medium oocysts was observed by 6 wk (unmedicated birds and birds given NIC or RESULTS HAL) and 8 wk (birds given ROB). Large oocysts (E. maxima) were present in the litter Live Performance of the unmedicated controls at 3 wk. Few large oocysts were found in the medicated At 6 wk of age, birds that had been groups. There was no significant difference medicated with NIC, HAL, and ROB in the number of oocysts before and after weighed significantly more than the un- withdrawal of medication. medicated controls (Table 1). Birds medicated with ROB weighed more at 3 wk than birds given HAL, and birds given HAL Effects of Challenge weighed more than birds given NIC, but by The weight gains of the challenged 6 wk there were no significant differences controls were significantly lower than that among drugs. There were no significant of the unchallenged controls, indicating differences in body weight at 7 or 8 wk, or in that they were susceptible to all three weight gain during the withdrawal periods species (Table 4). By contrast, the weight
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or 10,000 oocysts of E. tenella. Birds were weighed 7 days postinoculation and weight gain was calculated. Forty-eight birds from the same hatch as the principal study were reared to 6 wk of age on new litter in a separate accommodation. They were given ROB as an additional assurance against the possibility of exposure to infection and served as challenged and unchallenged susceptible controls.
(6 to 7, 7 to 8, or 6 to 8 wk; data not shown), irrespective of the medication regimen employed. At 6, 7, and 8 wk of age, birds that had been medicated with NIC, HAL, and ROB had a significantly lower feed conversion than the unmedicated controls (Table 1). There were no significant differences in feed conversion among the medicated groups at 6 or 7 wk. At 8 wk, birds that had been given NIC and LAS (Treatment IB) had a lower feed conversion than birds given HAL and LAS (Treatment 2A). No significant differences in feed conversion were observed during the withdrawal periods (6 to 7, 7 to 8, or 6 to 8 wk; data not shown). No significant differences in feed intake or mortality were found (data not shown). Mortality (mean = 11.9%) was primarily due to ascites (68% of birds examined) and handling during weighing.
EFFECTS OF DRUGS UPON BROILERS
661
TABLE 1. The effects of various shuttle programs upon the body weight and feed conversion of broilers Body weight Treatment
1
3 wk
6 wk
6 wk
670'b 696 722a 668c
2,279* 2,254" 2,275" 2,192b 15 Body weight
7 wk
8 wk
2,737 2,784 2,759 2,744 2,795 2,756 2,750 25
3,225 3,225 3,214 3,225 3,250 3,222 3,243 37
1.407* 1.693b 1.3741": 1.713b 1.693b 1.352": 1.763" 1.428" .014 .008 Feed conversion 7 wk b
1.833 1.812" l,846 b 1.828b 1.817b 1.830b 1.874" .012
8 wk 1.939bc 1.928c 1.963" 1.932bc 1.933bc 1.942"c 1.981" .010
a_c
Means within columns with no common superscripts differ significantly (P < .05). Birds had been raised on nicarbazin (NIC), halofuginone (HAL), or robenidine (ROB) from 0 to 3 wk, lasalocid from 3 to 7 wk (Treatment A, 1-wk withdrawal) or 3 to 6 wk (Treatment B, 2-wk withdrawal), or no drug throughout (NONE). J
gains of birds from all three medicated treatments were not significantly different from the unchallenged controls, indicating that they were immune to the challenge infection. DISCUSSION
When included in the starter feed for the first 3 wk, NIC, HAL, and ROB were effective in preventing lesions due to coccidiosis. Control of infection was not complete, however, as some oocysts were found in scrapings from the intestines, and oocysts (small and medium) were present in the litter. The effects of the coccidial infection upon body weight (6 wk) and feed conversion (6, 7, and 8 wk) were apparent: medicated birds showing heavier weights and lower feed conversions than the unmedicated controls. No effects upon feed intake or mortality were observed. At 3 wk, birds given HAL and ROB weighed more than birds given NIC but there were no significant differences in body weight between any of the medica-
tion regimes thereafter. There were no significant differences in feed conversion among medicated groups at 3, 6, or 7 wk of age, irrespective of whether NIC, HAL, or ROB had been used in the starter feed. There were no significant differences in feed intake, weight gain, or feed conversion whether medication was withdrawn from 6 to 7, 7 to 8, or 6 to 8 wk of age.
TABLE 2. Lesions and presence of oocysts in the intestines of broilers
Treatment1
Lesion score
Scrapings 2
1 2 3 4
0 0 0 1.5
6/12 6/12 2/12 2/4
(NIC) (HAL) (ROB) (NONE)
(+) (+) (+) (+++)
JBirds had been raised on nicarbazin (NIC), halofuginone (HAL), or robenidine (ROB) from 0 to 3 wk or no drug (NONE). 2 Number of birds positive for oocysts in the duodenum and mid intestine/total number of birds. A subjective assessment of the numbers present is given in parentheses. +++, many; +, few.
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1A IB 2A 2B 3A 3B 4 Pooled SE
3 wk
teg)
(g) 1 (NIC) 2 (HAL) 3 (ROB) 4 (NONE) Pooled SE
Feed conversion
662
CHAPMAN AND HACKER TABLE 3. Oocysts of Eitneria species present in the litter of broilers Small and medium oocysts
Treatment 1
3 wk
6 wk
7 wk
8 wk
Large oocysts 3 wk
6 wk
7 wk
8 wk
2a 0a 0" la la 0a 0b
0* la
o*a
oi a*
o»a
3
1A (NIC) IB 2A (HAL) 2B 3A (ROB) 3B 4 (NONE)
147" 139" 190" 152* 112* 90* 231"
34 b 104b 27b 23 b 4 2 ab 3 7 ab
31b
59 b 37bc 23 b 2ib 47ab 31 a b 29b
(Oocysts/g x 10- ) 9b 0a 8C 0* 4a 5b llb 3* 12 b 0a 10 b 0* 8b 24a
0
0 0* 0a 0b
a
0 0a ib
a_c
There have been no other published comparisons of the effects of shuttle programs comprising NIC, HAL, or ROB in the starter and LAS in the grower feed, with different withdrawal periods, upon the growth of broilers. A progressive decrease was observed in the number of small and medium and in large oocysts (unmedicated controls) in the litter. There have been few studies of the numbers of oocysts present in broiler house litter where shuttle programs have been employed. An increase in small and medium oocysts was found by 5 and 7 wk, respectively, at two commercial broiler houses where NIC was followed by salinomycin (Chapman, 1992). The num-
ber of oocysts present at 3 wk, however, was substantially less than in the present study, in which an infection was intentionally introduced. There was no increase in small and medium, or in large oocysts after withdrawal of medication. In a study conducted at 46 commercial broiler houses, in which birds were given a shuttle program comprising HAL in the starter and LAS or salinomycin in the grower feed, a decrease in the number of small oocysts was observed following withdrawal of medication, but numbers of medium oocysts were unchanged (Chapman and Johnson, 1992). Large oocysts were few in number, but a slight increase occurred following withdrawal of drug.
TABLE 4. Effects of challenging 6-wk-old birds 'with oocysts of three species of Eitneria on weight gain from days 0 to 7 postinoculation Challenge inoculum Source of birds
1
E.. tenella
E. acervulina
449a 456a 444a 21711 478a 35
505 a 498 a 432a
E. maxima
(g) Treatment 1 (NIC) Treatment 2 (HAL) Treatment 3 (ROB) Challenged controls Unchallenged controls Pooled SEM a b
478 a 33
463 a 399a 448 a 156fc 478* 34
' Means within columns with no common superscripts differ significantly (P < .05). Birds had been reared on nicarbazin (NIC), halofuginone (HAL), or robenidine (ROB) from 0 to 3 wk, and lasalocid from 3 to 6 wk. a
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Means within rows for each treatment with no common superscripts differ significantly (P < .05). SE = 20.8, small and medium oocysts; SE = 2.3, large oocysts. 1 Birds had been raised on nicarbazin (NIC), halofuginone (HAL), or robenidine (ROB) from 0 to 3 wk, lasalocid from 3 to 7 wk (Treatment A, 1-wk withdrawal) or 3 to 6 wk (Treatment B, 2-wk withdrawal), or no drug throughout (NONE).
EFFECTS OF DRUGS UPON BROILERS
cient exposure to infection occurred to permit the induction of immunity. ACKNOWLEDGMENTS This work was supported by a grant from Hoffmann-La Roche, Inc., Nutley, NJ 07110. The assistance of Z. B. Johnson is gratefully acknowledged.
REFERENCES Chapman, H. D., 1992. Research note: Immunity to Eimeria spp. in broilers reared on nicarbazin and salinomycin. Poultry Sci. 71:577-580. Chapman, H. D., and Z. Johnson, 1992. Oocysts of Eimeria in the litter of broilers reared to eight weeks of age before and after withdrawal of lasalocid or salinomycin. Poultry Sci. 71: 1342-1347. Johnson, J., and W. M. Reid, 1970. Anticoccidial drugs: lesion scoring techniques in battery and floor-pen experiments with chickens. Exp. Parasitol. 28:30-36. Long, P. L., R. V. Tompkins, and B. J. Millard, 1975. Coccidiosis in broilers: evaluation of infection by the examination of broiler house litter for oocysts. Avian Pathol. 4:287-294. McDougald, L. R., and W. M. Reid, 1971. Susceptibility of broilers to coccidiosis following early coccidiostat withdrawal. Poultry Sci. 50: 1164-1170. National Research Council, 1984. Nutrient Requirements of Poultry. 8th rev. ed. National Academy Press, Washington, DC. SAS Institute, 1988. SAS/STAT® User's Guide. SAS Institute Inc., Cary, NC.
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According to Long et al. (1975) one factor that may contribute to a decrease in oocyst numbers in the litter of older birds is the development of immunity. Immunity is important in broilers if long withdrawal periods are employed because clinical coccidiosis could occur following withdrawal of drug (McDougald and Reid, 1971). Birds from two commercial farms reared on a shuttle program comprising NIC followed by salinomycin were immune to E. acervulina and £. maxima (judged by weight gain), but birds from only one of the farms had developed immunity to E. tenella (Chapman, 1992). In this study, birds taken from the various treatments at 6 wk of age were challenged with either E. acervulina, E. maxima, or E. tenella. Their weight gains were not significantly different from that of the unchallenged controls, indicating that they had developed immunity to these species despite having received anticoccidial medication. The development of immunity may partly explain the decline in oocyst numbers during the trial and the failure to observe an increase in oocyst numbers following withdrawal of medication. The development of immunity to E. maxima was more surprising because few oocysts of this species were seen in the litter. Eimeria maxima, however, is highly immunogenic, and evidently suffi-
663
1993 Poultry Science 72:658-663
INTRODUCTION
Shuttle programs, in which two or more anticoccidial drugs are included in the feed during the life of a single flock of birds, are widely used in broiler production. Despite this, there is little published information upon the efficacy of such programs for the control of coccidiosis. In this study, the efficacy of nicarbazin, halofuginone, or robenidine in the starter feed, followed by the ionophore lasalocid in the grower ration, was investigated. A current practice when rearing broilers to 8 wk is to remove the anticoccidial drug from the diet approximately 2 wk
prior to slaughter (Chapman and Johnson, 1992). The effect of withdrawing medication for 1 or 2 wk upon the growth of broilers reared on lasalocid is not known and was, therefore, examined. Coccidiosis may occur following withdrawal of anticoccidial drugs, and, therefore, acquisition of immunity is desirable if long withdrawal periods are employed (McDougald and Reid, 1971). Birds reared on a shuttle program comprising nicarbazin and salinomyrin developed immunity to certain species of Eimeria (Chapman, 1992). A further objective was to investigate the development of immunity in birds reared on nicarbazin, halofuginone, or robenidine followed by lasalocid. MATERIALS AND METHODS
Received for publication October 5, 1992. Accepted for publication November 20, 1992. iPublished with the approval of the Director, Arkansas Agricultural Experiment Station. 2 Cobb 500, Cobb-Vantress, Inc., Siloam Springs, AR 72764.
Birds and Housing
Day-old male chicks of a commercial broiler strain2 were obtained from a local
658
Downloaded from http://ps.oxfordjournals.org/ at New York University on May 2, 2015
ABSTRACT A floor-pen trial was conducted to investigate the effects of different shuttle programs upon the growth of broilers to 8 wk of age. Nicarbazin, halofuginone, and robenidine, when included in the starter feed for 3 wk, were effective in preventing lesions due to Eimeria. The effects of medication upon performance were apparent, medicated groups gaining more weight by 6 wk and having a lower feed conversion at 6, 7, and 8 wk than the unmedicated controls. There were no significant differences in body weight at 6, 7, or 8 wk or feed conversion at 6 or 7 wk among the medicated groups, whether medication was withdrawn for 7 or 14 days. A decrease in the number of small and medium oocysts in the litter was observed as the trial progressed. Few large oocysts (Eimeria maxima) were seen in the medicated groups. Numbers of oocysts did not increase following withdrawal of medication. Birds from all medicated groups were challenged at 6 wk with oocysts of Eimeria acervulina, Eimeria maxima, or Eimeria tenella. Weight gains were similar to that of the unchallenged controls, indicating that they had acquired immunity to these species of Eimeria. (Key words: coccidiosis, shuttle program, immunity, oocysts, withdrawal of drug)
EFFECTS OF DRUGS UPON BROILERS
659
Twelve pens were randomly allocated to Treatments 1, 2, and 3, and four pens to Treatment 4. Treatments 1, 2, and 3 were given nicarbazin3 (NIC, 125 mg/kg), halofuginone 4 (HAL, 3 mg/kg), or robenidine5 (ROB, 33 mg/kg), respectively, from 0 to 3 wk, and lasalocid° (LAS, 99 mg/ kg) from 3 to 6 wk. Six pens that had been randomly preselected from each of these treatments were given lasalocid from 6 to 7 wk followed by no drug from 7 to 8 wk (designated Treatments 1A, 2A, and 3A, respectively; 1 wk of withdrawal). The remaining six pens in each treatment were given no drug from 6 to 8 wk (Treatments IB, 2B, and 3B; 2 wk of withdrawal). Treatment 4 was an unmedicated control given no drugs throughout. Roxarsone7 was included in the diet of all birds at 50 mg/kg from 0 to 6 wk.
Parasites
At 2 wk, birds were infected by including a mixture of sporulated oocysts of Eimeria acervulina, Eimeria maxima, and Eimeria tenella directly in a small quantity of feed. A total of 100,000 E. acervulina, 10,000 E. maxima, and 10,000 £. tenella were provided per bird. Oocysts were recent field isolates obtained from local broiler farms. Lesions
One bird was removed at random from each pen at 20 days (6 days after infection), necropsied, and the intestines examined for lesions due to coccidiosis by the method of Johnson and Reid (1970). The presence of oocysts of Eimeria in scrapings of the duodenum and midintestine was also recorded.
Feed
The basal diet was formulated to meet the nutritional requirements of the broiler
Oocysts in the Litter
Numbers of oocysts present in samples of litter were determined at 3,6,7, and 8 wk. Approximately 10 handfuls of surface litter were taken from four preselected pens from 3 Nicarb®, MSD AgVet, Division of Merck and Co., each treatment and placed in a plastic bag. Inc., Rahway, NJ 07065. 4 Stenorol®, Hoechst-Roussel Agri-Vet Co., The litter was weighed and suspended in 600 mL of tap water, and the oocysts Somerville, NJ 08876. 5 Robenz, American Cyanamid Co., Agricultural counted as described by Chapman (1992). Division, Wayne, NJ 07470. Oocysts were classified as either small (E. 6 Avatec®, Hoffmann-La Roche Inc., Nutley, NJ acervulina or Eimeria mitis), medium (possi07110. 7 3-Nitro®, Salsbury Laboratories, Inc., Charles City, bly E. tenella, Eimeria necatrix, or Eimeria praecox), or large (E. maxima). IA 50616.
Downloaded from http://ps.oxfordjournals.org/ at New York University on May 2, 2015
hatchery and assigned randomly to each of chicken (National Research Council, 1984). 40 pens (46 birds per pen). The chicks were Starter, grower, and finisher feeds were placed on new rice hulls to provide about 5 given from 0 to 3, 4 to 6, and 7 to 8 wk, to 10 cm of absorbent dry litter. Each pen respectively. A composite sample of feed was equipped with two tubular hanging was retained from each batch of feed and feeders and an automatic waterer. Ther- assayed for the concentration of drugs. mostatically controlled gas brooders and Analyses indicated that levels of the anventilation fans were used to regulate ticoccidials were within acceptable limits of temperature, and 23 h of light and 1 h of the intended concentrations. darkness was provided each day. The chicks had been vaccinated against Newcastle, Marek's, and infectious bursal Performance Data disease at the hatchery. For the 1st wk any Composite pen body weight was obbirds that died or were unable to feed tained at 3, 6, 7, and 8 wk, and total feed properly were replaced. Birds had free consumed was recorded for each age access to feed and water throughout the period. All birds that died were weighed experiment. and their body weight used to calculate feed conversion (feed consumed per unit of gain). Trial Design
660
CHAPMAN AND HACKER
Challenge Three birds were removed from each pen when the birds were 6 wk old, transferred to a clean pen, and given unmedicated feed. Three days later, each bird was weighed and challenged with either 100,000 oocysts of E. acervulina, 11,500 oocysts of E. maxima,
Statistical Analysis
Performance data for four pens (Treatment 4), 12 pens (Treatments 1,2, and 3) or six pens (Treatments 1 A, IB, 2A, 2B, 3A, and 3B) were combined for analysis. When significant treatment effects were observed, means were separated by repeated t tests using probabilities generated by the Least Squares Means option of the General Linear Models (GLM) procedure of the SAS Institute (1988). To examine differences in oocyst numbers, a split-plot design was used. When significant age by treatment interactions were observed, age means within treatments were separated using the method of least square differences.
Lesions
Lesions were found in the unmedicated controls but not in the medicated groups. A few oocysts were found in the intestines of medicated birds (Table 2). Oocysts in the Litter
Numbers of oocysts present in the litter are given in Table 3. No differences in the number of small and medium, or the number of large oocysts were found among the medicated groups (P > .05). A significant decrease in the numbers of small and medium oocysts was observed by 6 wk (unmedicated birds and birds given NIC or RESULTS HAL) and 8 wk (birds given ROB). Large oocysts (E. maxima) were present in the litter Live Performance of the unmedicated controls at 3 wk. Few large oocysts were found in the medicated At 6 wk of age, birds that had been groups. There was no significant difference medicated with NIC, HAL, and ROB in the number of oocysts before and after weighed significantly more than the un- withdrawal of medication. medicated controls (Table 1). Birds medicated with ROB weighed more at 3 wk than birds given HAL, and birds given HAL Effects of Challenge weighed more than birds given NIC, but by The weight gains of the challenged 6 wk there were no significant differences controls were significantly lower than that among drugs. There were no significant of the unchallenged controls, indicating differences in body weight at 7 or 8 wk, or in that they were susceptible to all three weight gain during the withdrawal periods species (Table 4). By contrast, the weight
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or 10,000 oocysts of E. tenella. Birds were weighed 7 days postinoculation and weight gain was calculated. Forty-eight birds from the same hatch as the principal study were reared to 6 wk of age on new litter in a separate accommodation. They were given ROB as an additional assurance against the possibility of exposure to infection and served as challenged and unchallenged susceptible controls.
(6 to 7, 7 to 8, or 6 to 8 wk; data not shown), irrespective of the medication regimen employed. At 6, 7, and 8 wk of age, birds that had been medicated with NIC, HAL, and ROB had a significantly lower feed conversion than the unmedicated controls (Table 1). There were no significant differences in feed conversion among the medicated groups at 6 or 7 wk. At 8 wk, birds that had been given NIC and LAS (Treatment IB) had a lower feed conversion than birds given HAL and LAS (Treatment 2A). No significant differences in feed conversion were observed during the withdrawal periods (6 to 7, 7 to 8, or 6 to 8 wk; data not shown). No significant differences in feed intake or mortality were found (data not shown). Mortality (mean = 11.9%) was primarily due to ascites (68% of birds examined) and handling during weighing.
EFFECTS OF DRUGS UPON BROILERS
661
TABLE 1. The effects of various shuttle programs upon the body weight and feed conversion of broilers Body weight Treatment
1
3 wk
6 wk
6 wk
670'b 696 722a 668c
2,279* 2,254" 2,275" 2,192b 15 Body weight
7 wk
8 wk
2,737 2,784 2,759 2,744 2,795 2,756 2,750 25
3,225 3,225 3,214 3,225 3,250 3,222 3,243 37
1.407* 1.693b 1.3741": 1.713b 1.693b 1.352": 1.763" 1.428" .014 .008 Feed conversion 7 wk b
1.833 1.812" l,846 b 1.828b 1.817b 1.830b 1.874" .012
8 wk 1.939bc 1.928c 1.963" 1.932bc 1.933bc 1.942"c 1.981" .010
a_c
Means within columns with no common superscripts differ significantly (P < .05). Birds had been raised on nicarbazin (NIC), halofuginone (HAL), or robenidine (ROB) from 0 to 3 wk, lasalocid from 3 to 7 wk (Treatment A, 1-wk withdrawal) or 3 to 6 wk (Treatment B, 2-wk withdrawal), or no drug throughout (NONE). J
gains of birds from all three medicated treatments were not significantly different from the unchallenged controls, indicating that they were immune to the challenge infection. DISCUSSION
When included in the starter feed for the first 3 wk, NIC, HAL, and ROB were effective in preventing lesions due to coccidiosis. Control of infection was not complete, however, as some oocysts were found in scrapings from the intestines, and oocysts (small and medium) were present in the litter. The effects of the coccidial infection upon body weight (6 wk) and feed conversion (6, 7, and 8 wk) were apparent: medicated birds showing heavier weights and lower feed conversions than the unmedicated controls. No effects upon feed intake or mortality were observed. At 3 wk, birds given HAL and ROB weighed more than birds given NIC but there were no significant differences in body weight between any of the medica-
tion regimes thereafter. There were no significant differences in feed conversion among medicated groups at 3, 6, or 7 wk of age, irrespective of whether NIC, HAL, or ROB had been used in the starter feed. There were no significant differences in feed intake, weight gain, or feed conversion whether medication was withdrawn from 6 to 7, 7 to 8, or 6 to 8 wk of age.
TABLE 2. Lesions and presence of oocysts in the intestines of broilers
Treatment1
Lesion score
Scrapings 2
1 2 3 4
0 0 0 1.5
6/12 6/12 2/12 2/4
(NIC) (HAL) (ROB) (NONE)
(+) (+) (+) (+++)
JBirds had been raised on nicarbazin (NIC), halofuginone (HAL), or robenidine (ROB) from 0 to 3 wk or no drug (NONE). 2 Number of birds positive for oocysts in the duodenum and mid intestine/total number of birds. A subjective assessment of the numbers present is given in parentheses. +++, many; +, few.
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1A IB 2A 2B 3A 3B 4 Pooled SE
3 wk
teg)
(g) 1 (NIC) 2 (HAL) 3 (ROB) 4 (NONE) Pooled SE
Feed conversion
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CHAPMAN AND HACKER TABLE 3. Oocysts of Eitneria species present in the litter of broilers Small and medium oocysts
Treatment 1
3 wk
6 wk
7 wk
8 wk
Large oocysts 3 wk
6 wk
7 wk
8 wk
2a 0a 0" la la 0a 0b
0* la
o*a
oi a*
o»a
3
1A (NIC) IB 2A (HAL) 2B 3A (ROB) 3B 4 (NONE)
147" 139" 190" 152* 112* 90* 231"
34 b 104b 27b 23 b 4 2 ab 3 7 ab
31b
59 b 37bc 23 b 2ib 47ab 31 a b 29b
(Oocysts/g x 10- ) 9b 0a 8C 0* 4a 5b llb 3* 12 b 0a 10 b 0* 8b 24a
0
0 0* 0a 0b
a
0 0a ib
a_c
There have been no other published comparisons of the effects of shuttle programs comprising NIC, HAL, or ROB in the starter and LAS in the grower feed, with different withdrawal periods, upon the growth of broilers. A progressive decrease was observed in the number of small and medium and in large oocysts (unmedicated controls) in the litter. There have been few studies of the numbers of oocysts present in broiler house litter where shuttle programs have been employed. An increase in small and medium oocysts was found by 5 and 7 wk, respectively, at two commercial broiler houses where NIC was followed by salinomycin (Chapman, 1992). The num-
ber of oocysts present at 3 wk, however, was substantially less than in the present study, in which an infection was intentionally introduced. There was no increase in small and medium, or in large oocysts after withdrawal of medication. In a study conducted at 46 commercial broiler houses, in which birds were given a shuttle program comprising HAL in the starter and LAS or salinomycin in the grower feed, a decrease in the number of small oocysts was observed following withdrawal of medication, but numbers of medium oocysts were unchanged (Chapman and Johnson, 1992). Large oocysts were few in number, but a slight increase occurred following withdrawal of drug.
TABLE 4. Effects of challenging 6-wk-old birds 'with oocysts of three species of Eitneria on weight gain from days 0 to 7 postinoculation Challenge inoculum Source of birds
1
E.. tenella
E. acervulina
449a 456a 444a 21711 478a 35
505 a 498 a 432a
E. maxima
(g) Treatment 1 (NIC) Treatment 2 (HAL) Treatment 3 (ROB) Challenged controls Unchallenged controls Pooled SEM a b
478 a 33
463 a 399a 448 a 156fc 478* 34
' Means within columns with no common superscripts differ significantly (P < .05). Birds had been reared on nicarbazin (NIC), halofuginone (HAL), or robenidine (ROB) from 0 to 3 wk, and lasalocid from 3 to 6 wk. a
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Means within rows for each treatment with no common superscripts differ significantly (P < .05). SE = 20.8, small and medium oocysts; SE = 2.3, large oocysts. 1 Birds had been raised on nicarbazin (NIC), halofuginone (HAL), or robenidine (ROB) from 0 to 3 wk, lasalocid from 3 to 7 wk (Treatment A, 1-wk withdrawal) or 3 to 6 wk (Treatment B, 2-wk withdrawal), or no drug throughout (NONE).
EFFECTS OF DRUGS UPON BROILERS
cient exposure to infection occurred to permit the induction of immunity. ACKNOWLEDGMENTS This work was supported by a grant from Hoffmann-La Roche, Inc., Nutley, NJ 07110. The assistance of Z. B. Johnson is gratefully acknowledged.
REFERENCES Chapman, H. D., 1992. Research note: Immunity to Eimeria spp. in broilers reared on nicarbazin and salinomycin. Poultry Sci. 71:577-580. Chapman, H. D., and Z. Johnson, 1992. Oocysts of Eimeria in the litter of broilers reared to eight weeks of age before and after withdrawal of lasalocid or salinomycin. Poultry Sci. 71: 1342-1347. Johnson, J., and W. M. Reid, 1970. Anticoccidial drugs: lesion scoring techniques in battery and floor-pen experiments with chickens. Exp. Parasitol. 28:30-36. Long, P. L., R. V. Tompkins, and B. J. Millard, 1975. Coccidiosis in broilers: evaluation of infection by the examination of broiler house litter for oocysts. Avian Pathol. 4:287-294. McDougald, L. R., and W. M. Reid, 1971. Susceptibility of broilers to coccidiosis following early coccidiostat withdrawal. Poultry Sci. 50: 1164-1170. National Research Council, 1984. Nutrient Requirements of Poultry. 8th rev. ed. National Academy Press, Washington, DC. SAS Institute, 1988. SAS/STAT® User's Guide. SAS Institute Inc., Cary, NC.
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According to Long et al. (1975) one factor that may contribute to a decrease in oocyst numbers in the litter of older birds is the development of immunity. Immunity is important in broilers if long withdrawal periods are employed because clinical coccidiosis could occur following withdrawal of drug (McDougald and Reid, 1971). Birds from two commercial farms reared on a shuttle program comprising NIC followed by salinomycin were immune to E. acervulina and £. maxima (judged by weight gain), but birds from only one of the farms had developed immunity to E. tenella (Chapman, 1992). In this study, birds taken from the various treatments at 6 wk of age were challenged with either E. acervulina, E. maxima, or E. tenella. Their weight gains were not significantly different from that of the unchallenged controls, indicating that they had developed immunity to these species despite having received anticoccidial medication. The development of immunity may partly explain the decline in oocyst numbers during the trial and the failure to observe an increase in oocyst numbers following withdrawal of medication. The development of immunity to E. maxima was more surprising because few oocysts of this species were seen in the litter. Eimeria maxima, however, is highly immunogenic, and evidently suffi-
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